546 Intelligence and Miscellaneous Articles 



A a 



'0 



like manner, the permanent but 

 somewhat lower temperature pos- 

 sessed by the interior of the ice. 

 The space, partly water, partly "^3 > 



ice, or partaking of the nature of ^ 

 each, MNOP, has a temperature 

 which varies from point to point, the portion NO corresponding 

 to what may be called the physical surface of the ice between AB 

 and ab, which is " plastic ice," or " viscid water," having the 

 most rapid variation of local temperature. 



II. Such a state of temperature, though it is in one sense perma- 

 nent, is so by compensation of effects. Bodies of different tempe- 

 ratures cannot continue so without interaction. The water ynust 

 give off heat to the ice, but it spends it in an insignificant thaw at 

 the surface, which there/ore wastes, even though the water be what is 

 called ice-cold, or having the temperature of a body of water enclosed 

 in a cavity of ice*. 



This waste has yet to be proved ; but I have little doubt of it ; and 

 it is confirmed bj^ the wasting action of superficial streams on the 

 ice of glaciers, though other circumstances may also contribute to 

 this effect. 



III. The theory explains " regelation." For let a second plane 

 surface of ice, A'B', be brought up to nearly physical contact with 

 the first surface, AB. There is a double film of " viscid water " 

 isolated between two ice surfaces colder than itself. The former 

 equilibrium is now destroyed. The films ABia and A'B'b'a' were 

 kept in a liquid or semiliquid state by the heat communicated to 

 them by the perfect water beyond. That is now removed, and the 

 film in question has ice colder than itself on both sides. Part of the 

 sensible heat it possesses is given to the neighbouring strata which 

 have less heat than itself, and the intercepted film of water in the 

 transition state becomes more or less perfect ice. 



Even if the second surface be not of ice, provided it be a bad con- 

 ductor, the effect is practically the same. For the film of water is 

 robbed of its heat on one hand by the colder ice, and the other 

 badly conducting surface cannot afford warmth enough to keep the 

 water liquid. 



This effect is well seen by the instant freezing of a piece of ice to 

 a worsted glove, even when on a warm hand. But metals may act 

 so, provided they are prevented from conveying heat by surrounding 

 them with ice. Thus, as has been shown, metals adhere to melting ice. 

 — Proc. Royal Society of Edinburgh. 



* I incline to think that water, in these circumstances, may, though sur- 

 rounded by ice, have a fixed temperature somewhat higher than what is called 

 32°. But I have not yet had an opportunity of verifying the conjectm-e. 



My idea is, that the invasion of cold from the surrounding ice is spent 

 in producing a very gradual " regelation " in the water which touches the 

 ice, leaving the interior water in possession of its full dose of latent heat, 

 and also of a temperature which may slightly exceed 32°. By similar rea- 

 soning, a small body of ice, enclosed in a large mass of water, will preserve 

 its proper internal temperature below 32° ; but, instead of regelation taking 

 place, the surface is being gradually thawed. This is the case contemplated 

 in the paragraph of the text to which this note refers. 



I 



